Regulated high-voltage power supply



1951 A. LE- R. OLSON 2,565,621

REGULATED HIGH-VOLTAGE POWER SUPPLY Filed Oct. 5, 1949 INVENTOR. ALTONLE ROY OLSON PWQ AJ Patented Aug. 28, 1951 2,565,621 REGULATEDHIGH-VOLTAGE POWER SUPPLY Alton Le Roy Olson, Lodi, N. J., assignor toAllen B. Du Mont Laboratories, Inc., Passaic, N. J., a

corporation of Delaware Application October 5, 1949, Serial No. 119,587

4 Claims.

My invention relates to electronic power supplies and more particularlyto regulated power supplies.

In power supplies where a high voltage of the order of 20,000 volts isdesired and where the current drawn from the supply is around 400microamperes, it is common practice to generate this voltage by means ofa so-called radio-frequency power supply comprising an oscillator, acomparatively low voltage power supply of the order of 300 volts outputto operate the oscillator, and a tuned circuit coupled to the oscillatorwith a detector to detect the high voltage appearing across the tunedcircuit. It is frequently desirable to maintain the output voltage asclose as possible to a fixed value while the current drawn from thesupply varies from about zero to 500 microamperes. In this case aregulator is necessary, and, if it is also desired to have the outputvoltage remain fixed as the A. C. line voltage supplying power to thelow voltage supply varies about its nominal value, it has heretoforebeen the practice to employ a second regulator to keep the outputvoltage of the low voltage supply at a fixed value.

It is one object of my invention to provide an improved power supply.

A second object is to provide an improved, regulated power supply.

A further object is to provide a regulator which will perform thefunctions of two regulators previously required as pointed out above.

Other objects will be apparent after a study of the specification anddrawing, in which;

The only figure is a schematic diagram of a i power supply employing theinvention.

A standard low voltage power supply I is shown having an output lead 2which conducts current to the screen grid of an amplifier tube 3 througha dropping resistor l, and to the plate of the amplifier tube 3 througha load resistor 5. .I he. lateof a tube 6 functioning as a variableimpedance is connected directly to the lead 2 and the plate Of anoscillator tube II is connected to the lead 2 through aradiofrequencychoke l and the inductance ll of a tuned circuit 9. A voltage dividercomprising a resistor 12 and a resistor I3 is connected between lead 2and ground.

A voltage regulator tube H such as a VR150 is connected between thescreen grid and cathode of the amplifier tube 3 which may be a 6AC'7.Another voltage regulator tube 16 is connected from the cathode of theamplifier tube 3 to round.

The oscillator tube II is connected in a tunedplate oscillator circuitalthough other types of oscillator circuits would work as well. Aportion 01' the energy of this tuned circuit 9, which comprisesinductance 8 in parallel with condenser I0, is picked up by the feedbackcoil is and applied to the grid of tube II by means of the RC couplingcircuit consisting of condenser is and resistor 2 I. The screen grid ofthe oscillator tube II is connected to the cathode of the variableimpedance tube 8. A bypass condenser 22 connects the grid and cathode ofthis variable impedance tube 8. The screen and plate supply voltages ofthe oscillator tube H are bypassed to ground by condensers 23 and 24respectively.

The high voltage rectifier section 25 consists of an inductance 26 whichis inductively coupled to inductance 3 and is generally wound on thesame coil form therewith. The inductance 28 has an inherent capacityindicated at 21, so that a parallel tuned circuit is formed. A voltagedoubling rectifier circuit comprises a pair of diodes 23 and 3|connected in the usual manner with a series capacitor 28 and a loadimpedance 32. A condenser 33 is connected in parallel with a voltagedivider, comprising a resistor 34 in series with a potentiometer 36,forming one current return path for the supply. The arm of thepotentiometer 36 is directly connected to the control grid of theamplifier tube 3. The common, low potential terminal of the inductancecoil 26, condenser 33 and potentiometer 36 is connected directly by aload 35 to the junction of a pair of resistors 12 and I3, connected inseries from the power supply lead 2 to ground.

In operation the power supply I supplies D. 0. power to the oscillatorwhich transforms it into A. C. power. The oscillator may be tuned byadjusting condenser ill, in order that the maximum voltage which isobtained at the frequency at which the inductance 26 resonates with theinherentcapacity 2.1, may be realized across the lead- 32. The voltagedoubler rectifier changes the A. C. voltage across the inductance 23into a D. C. voltage approximately equal to twice the peak value of saidA. C. voltage.

The power supply I also supplies power to the plate and screen gridcircuits of the amplifier tube 3. A current flows to ground through theplate load 5, through the tube 3 and through the constant voltage tubeI6, which furnishes a comparison voltage by holding the voltage at thecathode of tube 3 at a fixed potential. The arm of the voltage dividerpotentiometer 36 is ad- 3 justed so that the tube 3 operates essentiallyas a class A amplifier.

The variable impedance tube 6 operates in series between the powersupply i and the screen grid of the oscillator tube Ii. The impedance ofthis tube 6 is controlled by its grid potential, and since the grid ofthe tube is directly connected to the plate of the amplifier tube 3, anyvariation of the potential at the plate of the amplifier tube 3 producesvariation of the impedance of the tube 8.

An increase in the A. C. line voltage to the power supply I varies theoutput D. C. voltage on lead 2. A fixed percentage of this changeappears at the junction of resistors l2 and 13, thereby raising thepotential of the common terminal of inductance 26 and potentiometer 36.This in turn raises the potential of the arm of potentiometer 36 andmakes the grid of tube 3 more positive (or less negative) with respectto its cathode. More current flows through resistor 5, lowering /thepotential of the plate of tube 3 and the grid of tube 6. The impedanceof tube 6 consequently increases, and this results in a decrease of thescreen potential of tube II. If the resistors l2 and I3 have been chosento have the proper resistance, the screen voltage will decreasesufllciently to counteract the oscillator tube plate voltage increasedue to the line voltage increase. Therefore the voltage acrossinductance 26, and consequently across the load 32, will remainconstant. There is the same end result if the A. C. line voltage drops.

Most of the current of the high voltage supply normally flows from plateto cathode of the voltage doubler diode tube 3|, through load 32 toground, through resistor l3, and back through the inductance 26. Thusthe voltage across resistor l3 depends on the resultant of the currentof power supply I flowing therethrough in one direction and the currentof the high voltage rectifier flowing through it in the other direction.

The load 32 is shown as variable to indicate a varying impedance load.As the impedance of the load increases, the voltage thereacross wouldnormally increase except that the current through the load 32, theupward current through resistor 13, decreases. Thus the voltage at thejunction of resistors 12 and 13 increases, and the analysis of operationis the same as in the preceding case. The final result in the case of anincreasing impedance of load 32 is that the voltage on the screen gridof oscillator tube II is lowered, thereby decreasing the amplitude ofthe oscillations suihciently to maintain the voltage across the load 32at a fixed value.

Although I have described the invention in terms of a specificembodiment, it is obvious that modifications may be made within thescope thereof.

What I claimis:

1. A high-voltage power supply comprising a source of alternatingvoltage, a low-voltage power supply energized by said alternatingvoltage and having output terminals, a voltage divider across saidoutput terminals. an oscillator connected to and energized by said lowvoltage power supply, a tuned circuit coupled to said oscillator, saidtuned circuit having a plurality of terminals with a higher voltagebetween a pair. of said terminals than the voltage between the outputterminals oi. said low voltage power supply, a rectifier circuit torectify the high voltage between said pair of tuned circuit terminals,said rectifier circuit having a pair of output terminals and a voltagedivider therebetween, one of said output terminals being conductivelyconnected to one of said pair of tuned circuit terminals, a conductiveconnection between the tuned circuit terminal to which said rectifiercircuit output terminal is conductively connected and a tap on saidfirst-mentioned voltage divider, a vacuum tube having an input electrodeconnected to a tap on said second mentioned voltage divider, a source ofrelatively fixed voltage connected to a second electrode of said vacuumtube, and a plate circuit for said tube having current flow controlledby thevoltage difierence between said input and said second electrode,and a conductive connection between said plate circuit and saidoscillator.

2. A controlled direct current power supply comprising a first source ofD. C. voltage and an oscillator connected thereto and energized thereby,a rectifier circuit connected to said oscillator and energized thereby,said rectifier circuit providing a second source of direct current atthe output terminals thereof, a voltage divider connected across saidfirst source and a conductive connection from a tap thereon to one ofsaid output terminals of said rectifier circuit, a source of constantvoltage, a control amplifier connected to said rectifier circuit toderive voltage therefrom and to said source of constant voltage, saidamplifier being connected also to said first source of D. C. voltagetobe energized thereby and being controlled by the diiference in voltagebetween said constant voltage and said derived voltage, an outputterminal of said control amplifier being connected to said oscillator tocontrol the amplitude of oscillations thereof.

3. A controlled direct current power supply comprising a first source ofD. C. voltage and an all oscillator connected thereto and energizedthereby, a rectifier circuit connected to said oscillator and energizedthereby, said rectifier circuit providing a second source of directcurrent at the output terminals thereof, a first voltage dividerconnected across said output terminals, a second voltage dividerconnected across said first source, a conductive connection from a tapon said second voltage divider to a point on said first voltage divider,a source of constant voltage, a control tube having its plate circuitconnected to said first source of D. C. voltage to provide plate currenttherein and having one input electrode connected to a point on saidflrst voltage divider and a second input electrode connected to saidsource of constant voltage, said plate current being controlled by thedifi'erence in voltage between said constant voltage and the voltage atsaid point on said first voltage divider, said tube being connected tosaid oscillator to control the amplitude of oscillations therein.

4. The device of claim 3 in which the load circuit is connected betweena point on said first voltage divider and one terminal of said secondvoltage divider.

ALTON LE ROY OLSON.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED STATES PATENTS Number Name Date 2,386,548 Fogel Oct. 9, 19452,424,972 Dubin Aug. 5, 1947 2,485,652 Parker Oct. 25 1949 2,497,182Miller Feb. 14, 1950

